Radiation source and device

ABSTRACT

Radiation source ( 11 ) for electromagnetic radiation the major effective component of which is in the near-infrared region, in particular in the wavelength region between 0.8 μm and 1.5 μm, to form an elongated irradiation zone, with an elongated halogen lamp ( 11 ) comprising a glass body ( 14 ) that has a tubular shape with bases at the ends and contains at least one spiral filament ( 15 ), and with an elongated reflector ( 12 ), such that the bases ( 13 ) of the halogen lamp are disposed in the region of the reflector surface or behind it with reference to the position of the halogen lamp, wherein the ends of the halogen lamp are bent around toward the reflector and the spiral filaments or at least one of them is made thicker or is more densely wound in the bent region of the glass body, in such a way that the radiation flux density of the radiation source is substantially constant in the long direction of the source, between the outermost points of the bases.

[0001] The invention relates to a radiation source according to theprecharacterizing clause of claim 1 and to an arrangement forirradiation that incorporates such a radiation source.

[0002] Previous patent applications submitted by the present applicant,for example DE 197 36 462 A1, WO 99/42774 and P 10024731.8(unpublished), have disclosed methods for treating surfaces, processingmaterials and manufacturing composite materials that involved theemployment of electromagnetic radiation with a major effective componentin the near-infrared region, in particular in the wavelength regionbetween 0.8 μm and 1.5 μm. In several of these applications it isimportant for the irradiation to be incident upon a relatively widearea, to enhance the productivity of the method concerned. To achievethis goal, for the radiation source an elongated halogen lamp has beendesigned that comprises a glass tube with bases at the ends and at leastone spiral filament, as well as an elongated reflector.

[0003] In known radiation sources or irradiation apparatus withelongated lamps having bases at both ends—for instance, to be used formedical purposes or in illumination technology—the connectors or basesof such lamps are disposed coaxially at the ends of the glass tube; see,e.g., the patent documents U.S. Pat. No. 4,287,554 or DE 33 178 12 A1.These published documents also describe irradiation arrangements withseveral radiation sources disposed next to one another in parallel.

[0004] With a radiation source of this kind it is possible to irradiatea wide zone with a radiation flux density that is approximately constantover the entire width of the zone, which in turn makes the processingconditions uniform over a corresponding width of the material beingprocessed. However, at the ends of the halogen lamp, in the vicinity ofthe bases, the radiation flux density decreases, so that in theseregions other values of the process parameters apply. This isproblematic in the case of applications that require a constantradiation flux density over the whole width of the product, becausethese regions are in principle not functional, so that the usable widthof the irradiation zone, as far as processing technology is concerned,is smaller than the length of the radiation source.

[0005] Certain industrial processes that employ radiation in thenear-infrared region (“NIR radiation”) can in principle be carried outwith materials having very wide dimensions. However, to produceindividual halogen lamps of a correspondingly large width is technicallydifficult and extremely expensive. To implement such processes it wouldbe desirable to assemble several elongated halogen lamps having thestandard dimensions in lengthwise alignment with one another, so thatthe total length of the assembly of Lamps equals the length of the zoneto be irradiated. However, the above-mentioned fact that the radiationflux density decreases near the bases of the glass tube of an individualhalogen lamp proves to be a particularly severe problem in this regard.Hence the currently available radiation-source constructions cannot beemployed for such applications if it is essential that the radiationflux density be constant over the entire width of the processing region.

[0006] It is thus the objective of the present invention to disclose aradiation source of this generic kind that has been improved so as toproduce an irradiation zone with a width corresponding substantially tothe length of the radiation source, over which the radiation fluxdensity is substantially constant.

[0007] This objective is achieved by a radiation source with thecharacteristics stated in claim 1.

[0008] The invention on one hand includes the fundamental idea that theends of the lamp tube, regions in which it is of course impossible forradiation to be emitted, are repositioned so that they are behind—withrespect to the material or half-finished goods that are to betreated—the glass tube containing the spiral filament that emits the NIRradiation. The invention also includes the idea that this backwardrepositioning of the ends or connectors is achieved by bending the glasstube in the region near the ends.

[0009] Another idea included in the invention is that the spiralfilament or (if several filaments are present in the glass tube) atleast one spiral filament is made thicker in the above-mentioned regionnear the end, so that relatively more radiant energy in the NIR regionis emitted there. This measure counteracts the decrease in radiationflux density that would otherwise be expected near the ends as a resultof their backward displacement. The degree to which the filament is madethicker or more densely wound depends on the particular shape of theglass tube, specifically the radius of bending—an aspect that lieswithin the constructional judgement of a person skilled in the art, withsufficient guidelines obtainable from comparative tests with differentpatterns.

[0010] In an embodiment that is preferred because of its simplicity, atleast one end of the halogen lamp is bent with a radius of curvaturesuch that the end section is substantially at a right angle to thelongitudinal direction of the lamp. Hence the lamp connectors aredirected substantially at right angles to the longitudinal extent of thetube and the filament, so that it is a simple matter to position theconnectors in a row behind the linear array of halogen lamps.

[0011] In an alternative embodiment at least one end of the halogen lampcomprises a section bent into a C shape, so that the outermost point ofthe base associated with this end is displaced inward by a slight amountwith respect to the outermost point of the glass tube at this end. It isalso possible to construct halogen lamps with a glass tube having thislatter geometry at one end while the other end has the rectangularlybent configuration described above. The last-mentioned design enables(although with somewhat greater constructional effort regarding thehalogen lamp) an improved means of arranging the radiation sources“seamlessly” end to end in a row, in order to achieve an extremely wideirradiation field with almost completely constant radiation fluxdensity, because this design makes more space available for thestructures supplying power to the lamp bases.

[0012] The ends of the halogen lamp are advantageously in thermallyconducting contact with the reflector, and/or the bases are providedwith cooling means to dissipate heat. As a result, there is a steeptemperature (T) gradient between each of the curved regions of the glasstube and the adjacent connection region. In particular, a temperaturedecrease from more than 600° C. in the main body of the tube to aconnector or end temperature well below 300° C., in particular below200° C., is produced so that allowance is made for the thermalsensitivity of the ends of the lamps.

[0013] The above-mentioned cooling means in a first special embodimentcomprise heat-radiating surfaces (“flags”) at the ends of the lamp.Additionally or alternatively, plug-type bases are provided with specialheat-conducting means to transfer heat to the reflector (which as a ruleis essentially completely metallic and hence conducts heat away verywell).

[0014] Still more efficient, although requiring more elaboratetechnology, is to employ a pressurized fluid coolant to carry the heataway from the lamp ends. For this purpose the cooling means compriseflow channels through which the coolant passes to the ends or nearbyregions of the halogen lamp, and/or to the regions of the associatedreflector that are near the lamp ends.

[0015] In particular there is provided in the reflector at least onecompressed-air flow channel with outlet openings (“nozzles”) directedtowards the ends of the halogen lamp, through which cold compressedair—or another coolant gas—is conducted into these regions. In apreferred embodiment of this idea a plurality of compressed-air flowchannels is provided in the reflector, each of which comprises outletopenings so disposed and constructed that the compressed air passingthrough them becomes turbulent around the ends or regions near the endsof the glass tube. This turbulent flow ensures reliable dissipation ofthe heat from all of the surface regions that are to be cooled.

[0016] Another preferred embodiment has water channels in the reflector,which pass through the reflector regions near the lamp bases. Throughthese channels cooling water is passed, which serves to cool both thereflector itself (which is directly exposed to radiation from the spiralfilament) and also the ends of the lamps, indirectly by way of thethermal conductance between reflector and lamp ends.

[0017] An especially advantageous way to dissipate heat is provided byreflectors constructed as massive extruded profiles of a material withhigh thermal conductivity, in particular aluminum or an aluminum alloy.The reason is that in such reflectors the flow channels for the coolantfluid (whether embodied as channels for compressed air or for water) canbe incorporated particularly easily, and the massive construction of thereflector endows it with a high heat capacity and thus contributestoward making the radiation of heat away from the radiation source moreuniform, even if there are slight inhomogeneities in the primaryradiation profile of the spiral filament or slight fluctuations in thesupplied voltage.

[0018] A reflector profile of this kind that provides especiallyadvantageous reflection properties, which contribute to a long workinglife of the halogen lamp, and is also especially easy to manipulate inan irradiation system with modular construction, has a cross-sectionalshape with a substantially rectangular external contour and asubstantially W-shaped reflector surface, such that in particular two orthree coolant flow channels are incorporated into the foot regionbetween the “W” and the rectangular external contour.

[0019] An irradiation arrangement employing the solution in accordancewith the invention comprises a plurality of radiation sources of thekind proposed here, at least two of which are lined up in a row, end toend. Thus the radiation flux density is substantially constant over theentire longitudinal extent of the lined-up radiation sources, from theoutermost point on the first radiation source in the row to theoutermost point on the last radiation source, at its opposite end. Anadvantageous implementation of an overall cooling system is obtained inan embodiment in which the coolant flow channels in the row of radiationsources are aligned with one another and connected to form continuousflow channels. Each of these has a connection element through whichcoolant is received, disposed at a first one in the row of radiationsources.

[0020] Such an irradiation arrangement can be used in particular for theNIR drying of lacquers or plastic coatings—specifically powderlacquers—as well as for manufacturing plastic laminates or the thermaltreatment (specifically drying and/or producing cross-linkage) ofthin-layer structures, especially thermally sensitive substrates in thearea of semiconductor and display technology, and also in otherapplications such that the implementation of wide irradiation zones withalmost ideally constant radiation flux density enhances the productivityof the procedure.

[0021] Other advantages and useful features of the invention will beapparent from the subordinate claims and from the following descriptionof preferred exemplary embodiments with reference to the figures,wherein

[0022]FIG. 1 shows part of an irradiation arrangement with a radiationsource according to a first embodiment of the invention, represented asa longitudinal section,

[0023]FIG. 2 shows part of an irradiation arrangement with a radiationsource according to a second embodiment of the invention, represented asa longitudinal section, and

[0024]FIG. 3 is a sketch representing the position dependence of theradiation flux density in the longitudinal direction of the irradiationarrangements according to FIG. 1 or 2.

[0025]FIG. 1 shows part of an NIR irradiation arrangement 10 fortechnological purposes, with a plurality of halogen filament lamps 11disposed in a row extending in their long directions and aligned withone another, with each of which there is associated an elongatedreflector 12 made of an aluminum extruded profile.

[0026] The basic structure of the reflector is known per se from theapplicant's patent document EP 0 999 724 A2 and hence is not explainedfurther here. In the following reference will be made only to specialcooling devices disposed in the interior or the vicinity of thereflector.

[0027] As can be seen in the figure, the halogen filament lamp 11 has aglass body in the shape of a tube 14, which contains in its center anelongated spiral filament 15 and has at each of its two ends a connectorpin 13. The lamp is operated at high voltage and therefore at anelevated operating temperature, above 2500° K and in particular above2900° K, so that the radiation it emits has its major component in thenear-infrared region, specifically in the wavelength region between 0.8μm and 1.5 μm. The glass tube 14 is bent near its ends to formapproximately a right angle, so that each of its connectors 13 isdisposed on an end section that extends approximately perpendicular tothe middle section of the tube. It can also be seen that the spiralfilament 15 is progressively thickened as it approaches the “angled”region, and/or its spiral structure is more densely wound.

[0028] Because of the bending of the glass tube 14 toward the reflectorand the associated connector, in combination with the thickened orcondensed structure of the spiral filament 15, the halogen filament lamp11 provides NIR radiation at a substantially constant radiation fluxdensity over its length up to the lateral end regions.

[0029] In this regard reference is made to FIG. 3, in which the dashedline shows the distribution of radiation flux density of twoconventional NIR lamps aligned end to end, whereas the positiondependence of the radiation flux density in the longitudinal directionof the irradiation arrangement 10 shown in FIG. 1 is indicated(schematically) by a dot-dash line. The proposed construction thusenables several radiation sources to be lined up so as to form alinearly extended irradiation arrangement with no substantial reductionof the flux density at the sites where the lamps adjoin one another.

[0030] In the interior of the reflector 12 a cooling-water channel 16 isprovided, to cool the reflector by passing water W through it. Near thereflector surface is disposed a compressed-air tubule 17 with airnozzles 18 positioned near the ends of the glass tubes 14 to which theconnectors are attached; the cold compressed air A emerging from thesenozzles impinges on this region of the glass tube. Because of thiscooling of the ends of the lamps, in combination with theheat-dissipation ability of the massive metal reflector, a steep Tgradient is produced. This gradient ensures that even though thetemperature of the glass tube can exceed 600° C., it is possible to keepthe ends of the tube at a temperature around or below 200° C., which isimportant for the working life of the radiation source.

[0031]FIG. 2 shows another exemplary embodiment of an irradiationarrangement 20, in which components with the same function as those inFIG. 1 are identified by reference numerals derived from those in FIG.1.

[0032] It is evident that the reflector 22 in this case extends only toa point below the central axis of the glass tube 24 and hence of thespiral filament 25; another difference from the arrangement 10 shown inFIG. 1 is that here a cooling-water channel 26 runs continuously throughthe row of reflectors 22.

[0033] Furthermore, there is a substantial difference in theconfiguration of the halogen filament lamp 21, in that the geometry ofthe bent region near the end of the lamp has been modified. Here thisregion is substantially C-shaped, as a result of which the connectors 23have been shifted inward with respect to the outermost points of theglass tube 24. This makes it possible, firstly, for the halogen lamps 21to be even more closely apposed to one another; in addition, relativelylarge-area cooling surfaces (flags) 29 can be provided at the connectors23. There are also provided, in the region where the ends of the lampspass through the body of the reflector, sleeves 30 that serve both astension equalizers and heat conductors, ensuring good heat transfer tothe body of the reflector.

[0034] These measures, taken together and with no recourse to devicesfor active cooling by compressed air, likewise produce a relativelysteep T gradient in the region of the lamp ends.

[0035] Because of the close apposition of the halogen lamps, which isenabled by the configuration of the glass tube shown in FIG. 2, incombination with the C-shaped configuration of the bent regions, it ispossible for the radiation flux density along the row of several apposedradiation sources to be made extremely uniform, as indicated (againschematically) by the continuous line in FIG. 3. This is achieved to acertain degree even without any additional thickening or more densewinding of the spiral filament 25 in the bent region of the lamp tube.

[0036] The implementation of the invention is not restricted to theexamples described above and the aspects emphasized here, but in thecontext of the claims is also possible in a large number of furthermodifications that are within the competence of a person skilled in theart.

LIST OF REFERENCE NUMERALS

[0037]10; 20 NIR irradiation arrangement

[0038]11; 21 Halogen filament lamp

[0039]12; 22 Reflector

[0040]13; 23 Connecting pin

[0041]14; 24 Glass tube

[0042]15; 25 Spiral filament

[0043]16; 26 Channel for cooling water

[0044]17 Compressed-air tubule

[0045]18 Air nozzle

[0046]29 Cooling surface (flag)

[0047]30 Sleeve

[0048] A Compressed air

[0049] W Water for cooling

1. Radiation source (11; 21) for electromagnetic radiation the majoreffective component of which is in the near-infrared region, inparticular in the wavelength region between 0.8 μm and 1.5 μm, to forman elongated irradiation zone, with an elongated halogen lamp (11; 21)comprising a glass body (14; 24) that has a tubular shape with bases atthe ends and contains at least one spiral filament (15; 25), and with anelongated reflector (12; 22), such that connectors (13; 23) of thehalogen lamp are disposed in the region of the reflector surface orbehind it with reference to the position of the halogen lamp,characterized in that the ends of the glass body are bent around towardthe reflector and the spiral filaments or at least one of them is madethicker or is more densely wound in the bent region of the glass body,in such a way that the radiation flux density of the radiation source issubstantially constant in the long direction of the source, between theoutermost points of the bases.
 2. Radiation source according to claim 1,characterized in that at least one end of the glass body (14) is bentwith a radius of curvature such that this end is at substantially aright angle with respect to the longitudinal extent of the body. 3.Radiation source according to claim 1 or 2, characterized in that atleast one end of the glass body (24) comprises a region bentsubstantially in a C shape, such that the outermost point of theconnector (23) associated with this end is shifted slightly inward incomparison to the outermost point of the glass body (24) at this end. 4.Radiation source according to one of the preceding claims, characterizedin that the ends of the halogen lamp (11; 21) are disposed in thermallyconductive contact with the reflector (12; 22) and/or cooling means (16,17, 18; 26, 29, 30) are disposed at the ends for heat dissipation suchthat a steep T gradient is produced between the curved regions of theglass body (14; 24) and the connector (13; 23) adjacent thereto in eachcase, in particular a T decrease from a glass-body temperature above600° C. to a base temperature below 300° C., specifically below 200° C.5. Radiation source according to claim 4, characterized in that thecooling means comprise heat-radiating surfaces (29) at the ends of thehalogen lamp (21).
 6. Radiation source according to claim 4 or 5,characterized in that the cooling means comprise coolant flow channels(16, 17) to conduct a coolant fluid that has been placed under pressureto the ends of the halogen lamp (11) or the regions near its ends,and/or to the regions of the reflector (12) that are adjacent thereto.7. Radiation source according to claim 6, characterized by at least onecompressed-air flow channel (17) in or near the reflector (12) withoutlet openings (18) directed toward the ends of the glass body. 8.Radiation source according to claim 7, characterized by a plurality ofcompressed-air flow channels (17) in the reflector (12), each of whichcomprises outlet openings (18) directed toward the ends of the halogenlamp (11), the outlet openings being so disposed and constructed thatthe compressed air they supply is made turbulent around the ends, or theregions near the ends, of the glass body (14) of the halogen lamp. 9.Radiation source according to one of the claims 6 to 8, characterized bywater channels (16; 26) in the reflector (12; 22) that pass through theregions of the reflector that are adjacent to the lamp ends. 10.Radiation source according to one of the preceding claims, characterizedby plug-contact bases (23) that are associated with heat-conductingmeans (29) to transfer heat into the reflector (22).
 11. Radiationsource according to one of the preceding claims, characterized in thatthe reflector (22) is constructed as a massive extruded profile made ofa material with high thermal conductivity, in particular aluminum or analuminum alloy.
 12. Radiation source according to claim 11 and one ofthe claims 6 to 10, characterized in that flow channels (26) for acoolant fluid are pressed into the extruded profile.
 13. Radiationsource according to claim 11 or 12, characterized in that thecross-sectional shape of the outer contour of the extruded profile issubstantially rectangular and the cross section of the reflector surfaceis substantially W-shaped, such that in particular two or threecoolant-fluid flow channels are pressed into the foot region of the “W”.14. Irradiation arrangement (10; 20) with a plurality of radiationsources (11; 21) according to one of the preceding claims, wherein atleast two of the radiation sources are disposed in a row in which theyare lined up end to end, characterized in that the radiation fluxdensity is substantially constant over the entire longitudinal extent ofthe row of radiation sources, between the outermost point of the firstsource and the outermost point at the opposite end of the last radiationsource in the row.
 15. Irradiation arrangement according to claim 14,characterized in that coolant-fluid flow channels (16; 26) associatedwith the row of radiation sources are aligned with one another andconnected together to form continuous flow channels, each of which has aconnection element (30) through which coolant fluid is supplied to afirst one of the radiation sources in the row.